The present invention relates to a control circuit for controlling a semiconductor component which comprises an emitter, a collector and a gate, the control circuit comprising a gate driver the output of which is connected to the gate of the semiconductor component to be controlled.
Currently used power semiconductors, such as IGB transistors, are components where turn-on and turn-off are so fast that for example when they are used in pulse width modulated frequency converters, voltage change rates with a value exceeding 10 volts per nanosecond may appear in the output voltage of the frequency converter. Such a change rate causes a significant strain on the load of the frequency converter. The frequency converter load is typically a motor, high voltage change rates thus causing a strain on the motor's winding insulation and strong voltage reflections in the motor cables. In addition, high change rates cause electromagnetic interference to radiate to the environment.
It is known to restrict the voltage change rates in power semiconductors by increasing the resistance of a gate resistor connected between the output of the gate driver controlling a semiconductor component and the gate of the semiconductor component to be controlled. This slows down the rate of increase of the power component's gate charge, whereby the gate voltage also increases slower. A shortcoming of this connection method is that it is dependent on the power component's properties and their distribution which makes the accuracy of the end result fairly poor. In addition, the resistance in the coupling unnecessarily increases losses.